which carabiners for anchors

[andrewmcleod]

This is a US safety board graph where they state that 60g for 3ms should be the limit for chest loading (seat belt). It is related to crush zones (more relevant to steel cars than elasticity), which would be the same thing as rope elasticity. It makes more sense to me that there should be a g limit for humans, which is not the same thing as max load (but is obviously related). Those force curves the guy has at high sampling rate could be converted to acceleration.

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There effectively is a g-force limit - and it is about 6g.
Take the 6kN limit permitted, divide by user mass e.g. 100kg for the class A rope tests, you get the acceleration which comes to (after dividing by gravity) about 6g.

 

[Fjell]

There effectively is a g-force limit - and it is about 6g.
Take the 6kN limit permitted, divide by user mass e.g. 100kg for the class A rope tests, you get the acceleration which comes to (after dividing by gravity) about 6g.

Yeah, which is why I am curious as to exactly what is going on. Pulling 6g is not a big deal in many other situations. So something else is going on with the way the system is interacting on the body, Maybe just a terrible way for the force to be applied to the body.

 

[andrewmcleod]

Yeah, which is why I am curious as to exactly what is going on. Pulling 6g is not a big deal in many other situations. So something else is going on with the way the system is interacting on the body, Maybe just a terrible way for the force to be applied to the body.

It all depends on the duration.
6g continuous is a lot...
Fighter jets typically max out at 9g before they break, but pilots have supportive seats, special pressurised leggings etc...
Dropping somehow in a harness where most of their body and critically their head is unsupported is a bad thing, so the forces people can manage will be much lower. I suspect a roped system will have longer near-peak force durations than a less damped system.

60g for more than a tiny fraction of a second is likely to turn you into a paste...

 

[andrewmcleod]

The average human head weighs 5kg. A 6g fall is like having a 25kg weight briefly attached to your head while you are falling (plus similar weights on the rest of your body)... Most hard climbing falls only generate a few kN at most (e.g. they really struggled to get > 4kN falls in that video and they looked very unpleasant)

 

[andrewmcleod]

The thing to Google is Eiband diagrams, it seems